- What is amortization?
- Amortization is the process of paying off a debt with regular fixed payments where each payment is split between interest (on the current outstanding balance) and principal (paying down the balance). Early payments are mostly interest; later payments are mostly principal. The full month-by-month split is called the amortization schedule.
- How is amortization calculated?
- The monthly payment uses the formula M = P × [r(1+r)^n] / [(1+r)^n − 1], where P is principal, r is monthly rate (annual ÷ 12), n is total months. For each month: interest = current balance × monthly rate, principal = monthly payment − interest, new balance = old balance − principal. The schedule above generates this row by row for every payment in the life of the loan.
- Why do early payments have more interest than principal?
- Because interest is calculated against the CURRENT balance, which is highest at the start of the loan. On a $200K mortgage at 6.5%, the first month's interest is $200K × 6.5%/12 ≈ $1,083, leaving only $181 going to principal out of a $1,264 payment. By month 200, the balance is much smaller, so interest is much smaller — and most of the payment goes to principal.
- How do extra payments affect my amortization?
- Every extra dollar applied to principal immediately reduces all future interest. On a $200K mortgage at 6.5% / 30 years: adding $100/month extra saves ~$54,000 in interest and pays off the loan ~4.5 years earlier. $200/month saves $90,000 and shaves 8 years off. The earlier in the loan you add extras, the bigger the impact — extras in year 1 have far more effect than extras in year 25.
- What's the difference between bi-weekly and monthly payments?
- Bi-weekly = paying half your monthly payment every two weeks. Since there are 26 bi-weekly periods per year, you make 26 half-payments = 13 effective monthly payments instead of 12. That extra payment goes 100% to principal, cutting ~5 years off a 30-year mortgage. WARNING: some lenders charge fees for bi-weekly programs. DIY equivalent: take your monthly payment, divide by 12, add that to each monthly payment — same effect, no fees.
- How do I read an amortization schedule?
- Each row is one payment. The columns: (1) Payment Number — which month of the loan. (2) Total Payment — the fixed monthly amount. (3) Interest — interest charged on the current balance. (4) Principal — amount applied to reducing the loan. (5) Balance — remaining debt after this payment. Watch how interest declines and principal grows from row to row — that's the amortization curve in action.
- When should I refinance my loan?
- The break-even rule: closing costs ÷ monthly payment savings = months to recoup the refi. Example: $6,000 closing costs, $199/month savings → 30-month break-even. Refi if you plan to stay in the home (or keep the loan) longer than the break-even. Otherwise the closing costs eat the savings. Bonus tip: refi to a SHORTER term, not just a lower rate — locking in a 15-year saves much more than dropping from 7% to 6% on the same 30-year.
- Does this calculator work for auto loans, student loans, and personal loans?
- Yes. The amortization formula is identical for all installment loans. Enter the loan amount, rate, and term — the schedule works for mortgages, auto loans (typical 36-84 months), federal student loans (standard 10 years, extended 25 years), private student loans (5-20 years), personal loans (2-7 years), and business term loans.
- What is negative amortization?
- Negative amortization happens when the monthly payment is too small to cover the interest charged, so the unpaid interest gets added to the balance and the balance GROWS instead of shrinks. It's rare in modern fixed-rate loans but can occur on graduated-payment mortgages, certain ARMs with payment caps, income-driven student loan repayment plans, and credit cards if you don't pay at least the interest charge. Standard amortizing loans avoid this by design.
- Can I export the amortization schedule?
- Yes. The calculator above provides CSV export (open in Excel/Google Sheets/Numbers for analysis or charting) and a print-friendly view for paper records. Useful for accounting, taxes, refinance comparison, or showing a lender exactly how you've been making extra payments.
- How do I calculate the interest for a specific month?
- Multiply the current outstanding balance by the monthly interest rate (annual rate ÷ 12). Example: $185,000 balance at 6.5% APR → $185,000 × (6.5% ÷ 12) = $185,000 × 0.005417 = $1,002 interest charged that month. The rest of your fixed monthly payment goes to principal. This is the calculation the schedule runs for every month of the loan.
- What's the difference between 15-year and 30-year amortization?
- On a $200K loan at typical rates: 15-year (~5.7%) costs ~$1,658/mo and ~$98K total interest. 30-year (~6.5%) costs ~$1,264/mo and ~$255K total interest. 30-year saves $394/month but costs $157K more over the life of the loan. Hybrid strategy: take the 30-year for flexibility, but pay it as if it were a 15-year by adding $394 extra to principal each month — you get the savings without the rigid monthly obligation.
- How accurate is this amortization calculator?
- The calculations use the standard mortgage/loan amortization formula that every bank and lender uses. Results are accurate to the penny. Your actual payment may differ slightly due to rounding conventions at your specific lender, plus property tax/insurance/HOA add-ons (for mortgages — this tool calculates the P&I portion only).
- Is this amortization calculator free?
- 100% free. No signup, no email required, no credit pull, no data sent to any server. Every calculation runs in your browser locally. Unlike Bankrate or NerdWallet which use 'free calculators' as lead-generation for mortgage lender partners, we don't route you anywhere or sell your data.
